Wikipedia
Tetramethylsuccinonitrile
Tetramethylsuccinonitrile or TMSN is an organic compound with the formula (C(CH)CN). Classified as a di[nitrile]], it is a colorless and odorless solid. TMSN is the by-product from the use of some radical initiators used in polymer manufacture.
TMSN is derived from 2,2'-azobis-isobutyronitrile:
(NC(CH)CN) → (C(CH)CN) + NAIBN is a common radical initiator in the manufacture of polyvinyl chloride polymers.